When I rendered my model with Cycles, it seemed to flatten out
Is this the issue you have mentioned?

A flat shaded model without shadows as shown in the image below.



Check your "Ambient Occlusion" option under the tab "World". If you have set its "Factor" value to a higher value like "1" you will face this issue.



Try unchecking the Ambient Occlusion option or turn the factor value down to a smaller value like 0.05 or so as required. This might help resolve the issue.



Furthermore, darken the background color towards black, otherwise the model receive equal amount of background light from all angles.

Use multiple (about 3 different) smaller stronger lamps opposed to a large lamp. A large lamp will generate soft shadow and large widely distributed highlights. Small lamps generate well defined falloffs and concentrated highlights.